Phonographic record



M5 124, 1932. AG 1,859,396

PHONOGRAPHIWRECORD Filed Aug.- 20. 1930 Inventbm 1 Girl @5238! Attorney:

Patented May 24, 1932 NT OFFICE cam. smar or mamm'nm-wnrnnor, GERMANY rnonoomnrc nnconn Application filed August 20, 1930, SeriaLNo.

Myprimary object is to provide a phonograph disk adapted to be recorded on an ordinary phonograph by the old acoustical method, that is, a disk made of metal, provided with a smooth helical groove ;and which, placedon the revolving turntable of an ordinary phonograph, will be recorded by means of the diaphragm and needle of the phonograph, the needle impressing in the said smooth groove the sound waves transmitted to the diaphragm from outside the phonograph.

Phono aphic records having guide grooves or the needle, and made of metal, for instance of zinc, copper, brass, nickel and the like, are known. Phonographic records made of a in use, because the sound curve impressions or on formed of diflerent layers 0 metal are also lmown, the thin upper layer of said records produced alvanoplastically from the negative form Eeing correspondingly re-inforced. The object of my present invention Is to provide a phonographic record with guide grooves formed of two superimposed metals of different hardness.

f soundcurves are recorded on a disc soft metal, the recording style will be deeply forced into the material owing to the amplitude of'movement imparted thereto. tained in this way will be rapidly serves as a guide groove for the needle which will be repeatedly forced into ,jhe soft metal. On the other hand if trials'are made for recording sound curves on a record disc made of,

le will produce either no y veg slight. impressions hard metal, the st on said record, so that sound will not at all be reproduced or onlyfvery weakly reproduced, the needle destroying however slowly the path of the sound curve.

My present invention aims to unite the advantages of the soft and. hard metals by the fact that the disc ser to receive the record and, provided with gui e grooves is formed recording style'may be However the record successfully obdestroyed out injuring the core of aluminum,

476,866, andin Germany Eebruary 8, 1929.

of two superimposed metals of unequal hardness in such a way that said disc will be formed of a softmetal base coated with a thin harder metal layer. The harder coating layer is on one hand so thin that in the 0 recording opega'tion the impressions of the made through said layer into the softer metal base, and on the other hand so hard that it will permit repeated use of the record without injury.

In the accompanying drawings: Fig. 1 is a cross section of a record disc accordin to my invention prior to the forma tion of t e needle guiding grooves thereon. I Said disc is made for instance of circular m shape and formed of an inner soft metal core a, the vopposite sides of which are coated with thin layers of hard metal 6. t

Fig. 2 shows also an enlarged cross section of the record disc, on which the needle guido5 ing grooves are formed by stamping, pressing and the like. I Fig. 3 i'san enlarged cross sectional view of the groove.

The soft metal core a may also be first provided with needle guiding grooves and then coated with a thin hard metal layerprior to the recording operation. The coating 6 (Fi 2) is so thin that the impressions 0 produced by the recording style in the recording operation will be made sufliciently deep into the soft metal core a (Fig. 3) withthin hard metal coating 1). By way of example,"I may form a base or elctro-plated with a 80 harder metalsuch as copper or nickel. Having now fully described my said invention, what I claim and desire to secure by Letters Patent, is: a 1. Theherein described process of forming a phonographic disk for recording and reproducing purposes, consisting iii provida" core of-"relativelyesoft metal formed a stylus-receivin groove, providing the core with a flexible t in hard metal surface I 2 Y a 1,859,396 t, Y

film conforming tothe groove, the hard metal surface film being of a character readily responsive to stylus recordingindentations for transmitting said indentations permanently 5 to thesoft' metalcore. without breaking through the hard metal.

2. A- phonographic record comprising a core ,ofsoft metal and a flexible thin hard metal surface film for the core, the surface film being readily responsive to stylus recording indentations, and insuringthatsuch indentations are transmitted to and remain permanently in the soft metal without rupture of the hard metal-film.

7 CARL JKGER. v 

